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Radio Frequency Exposure and Compliance Issues for a Shortwave May 2008

Matthew W. Folkert, MSEEE Stephen S. Lockwood, P.E. dTR/H&D Joint Venture A Joint Venture of the Consulting Engineering firms of duTreil Lundin & Rackley and Hatfield & Dawson. Radio Frequency Exposure and Compliance Issues for a Shortwave May 2008. HCJB - Pifo, Equador. HCJB - Pifo, Equador.

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Radio Frequency Exposure and Compliance Issues for a Shortwave May 2008

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  1. Matthew W. Folkert, MSEEE Stephen S. Lockwood, P.E. dTR/H&D Joint Venture A Joint Venture of the Consulting Engineering firms of duTreil Lundin & Rackley and Hatfield & Dawson Radio Frequency Exposure and Compliance Issues for a ShortwaveMay 2008 dTR/H&D Joint Venture

  2. dTR/H&D Joint Venture HCJB - Pifo, Equador

  3. dTR/H&D Joint Venture HCJB - Pifo, Equador

  4. dTR/H&D Joint Venture Presentation Outline • Scope of Work • Exposure Standards • Analytical Work • Measurement Program • Findings

  5. dTR/H&D Joint Venture Scope of Work • Conduct a Maximum Permissible Exposure Evaluation (MPE) of All IBB Transmitting Facilities • 16 Shortwave and Mediumwave Stations Worldwide • Limited to a Survey • Safety Seminar and Plan

  6. dTR/H&D Joint Venture IBB Stations Worldwide

  7. dTR/H&D Joint Venture Schedule of Site Visits • Delano - 1998 • Greenville – 2001 • Kavala, Rhodes & Kuwait - 2001 • Morocco - 2002 • Sao Tome - 2002 • Philippines - 2003 • Botswana - 2003 • Sri Lanka - 2005 • Germany – 2006 • Tinian - 2007 • Thailand - 2008

  8. dTR/H&D Joint Venture Analytical Work • Modeling Using NEC-2 • Curtain Antennas with Full Reflecting Screen • Rhombic Antennas • E and H Field 2 Meters Above Ground

  9. dTR/H&D Joint Venture Curtain Antenna : E-Field

  10. dTR/H&D Joint Venture Curtain Antenna : H-Field

  11. dTR/H&D Joint Venture Exposure Standards • IEEE • C95.1-2005 • ICNIRP(International Committee on Non-Ionizing Radiation Protection) • Guidelines For Limiting Exposure To Time-varying Electric, Magnetic and Electromagnetic Fields(up to 300 GHz) • OET(FCC Office of Engineering & Tech.) • Bulletin 65

  12. dTR/H&D Joint Venture IEEE Occupational Standards

  13. dTR/H&D Joint Venture IEEE Public Standards

  14. dTR/H&D Joint Venture RF Exposure Mechanisms • Exposure to radio frequency (RF) fields results in the absorption of energy in the body • The mechanism of this energy transfer is the body acting as an antenna or, for contact currents, a semiconductive load for an RF source (i.e.RF source can be a tower, antenna, guy wire, etc)

  15. dTR/H&D Joint Venture RF Exposure Mechanisms (continued) • The direct result is RF currents flowing in the body • If the currents are large enough the body temperature rises • At a certain rate of energy absorption biological effects also occur

  16. dTR/H&D Joint Venture The Electromagnetic Spectrum

  17. dTR/H&D Joint Venture Measurement Program • IEEE C95.3 Recommended Practice for the Measurements of Potentially Hazardous Electrical Fields – RF and Microwave • Spatial Averaged over vertical line from 0.2 m – 2.0 m • 20 cm from any object

  18. dTR/H&D Joint Venture Spatial Averaging Measure over the area of a Human Body

  19. dTR/H&D Joint Venture Equipment Used • NARDA Model 8718B Electromagnetic Radiation Survey Meter • E-Field Probe: 8742 • H-Field Probe: 8732 • Both “shaped” probes • Conforms to IEEE Occupational Standard

  20. dTR/H&D Joint Venture Equipment Used • Holaday Contact Current Meter • Clamp-on Current Transformer: HI-3702 • System Readout: HI-4416 • 1 mA to 1 A • 100 kHz to 100 MHz

  21. dTR/H&D Joint Venture Contact Current Physical Contact with a Conductive Material

  22. dTR/H&D Joint Venture Typical Data Sheet

  23. dTR/H&D Joint Venture Findings • Where would you expect to find high fields at a shortwave broadcasting facility?

  24. dTR/H&D Joint Venture Transmitter Building?

  25. dTR/H&D Joint Venture Control Room?

  26. dTR/H&D Joint Venture Switch Matrix?

  27. dTR/H&D Joint Venture Transmission Lines?

  28. dTR/H&D Joint Venture Baluns?

  29. dTR/H&D Joint Venture Antenna Ground Works?

  30. dTR/H&D Joint Venture Antenna Near Field?

  31. dTR/H&D Joint Venture Warning Signs

  32. dTR/H&D Joint Venture Conclusions • Closer to ground of RF conductors the higher exposure level • Under Baluns - • Open Wire Transmission Line • Antenna Ground Works • Areas in main beam of antennas for 100 kW or greater within 100 meters

  33. Questions? Matt Folkert – matt@dlr.com Stephen Lockwood - lockwood@hatdaw.com www.dlr.com & www.hatdaw.com dTR/H&D Joint Venture

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